In the 1960s when this poster was produced most mail was still sorted by hand but the Post Office was hatching an ambitious plan to reshape the entire network and it needed the public to change with them. A new breed of sorting office was being developed, filled with “coding desks” at which staff would operate keyboards in order to register the mail as it entered the system. Postcodes, which compressed the information in every address were key to making this new type of sorting office work.

A line of postmen operating coding desks at Croydon Head Post Office, 1969. (POST 118/5424)

Between 1966 and 1974 every address in the United Kingdom was given a postcode and this poster from 1968 was part of the accompanying publicity campaign. Royal Mail was still promoting the postcode using posters and other methods as recently as the 1990s, a reflection of how long it takes to effect major change. You can read more about postcoding in our blog post Publicising the postcode or in our article on Postcodes on our website.

Today’s episode of The Peoples Post explored the issue of modernising the Post Office, looking particularly at the development of postcodes.

In order for the introduction of postcodes to succeed the public needed to be willing to adopt them. Psychological studies showed that the best means of achieving this was for the postcodes to “compromise familiarity and brevity”[1]. Once a system of postcodes encompassing both these virtues was developed and rolled out, the next step was for the Post Office to publicise the new means of addressing the mail.

The Post Office invested heavily in a range of campaigns to increase the use of postcodes. In the late 1970s these campaigns were intended to “remind, not persuade people to use their postcodes”[2]. This recognised that the main reason for not using a postcode was forgetfulness, rather than outright resistance to postcodes.

One character helping promote postcodes in the 1980s was Poco the elephant. Although the use of an elephant in publicity campaigns played on people’s forgetfulness when using postcodes, Poco himself is well remembered by visitors to the Royal Mail Archive. In addition to this poster, we also have a range of other material produced as part of this campaign, including a pen, a sweatshirt, a badge, and a vinyl record (the Postcode Song, with Poco on the cover).

Poco the elephant says… (POST 110/3083)

Other campaigns, such as the one below from the 1970s, attempted to use storytelling as a means of increasing the use of postcodes. This style of poster gave more scope to explain why postcodes were important. The storytelling element also helped members of the public relate to familiar situations.

In this series of blog posts, Peter Sutton, PhD candidate researching the post-war history of technology and industrial relations in the British Postal Service, offers some reflections on the history of the modern postcode. The significance of the postcode and its origins in the post-1945 era are considered followed by some archival examples tracing different aspects of its design along its journey from a specialised engineering concept to a universally recognised geographical referencing tool.

As mentioned in previous posts, the GPO’s design of the modern postcode became, after the Second World War, a systematic, long-term project which was part of wider attempts at designing sorting machines for a future national sorting system based on new technology. The vision outlined by leading engineers and postal experts in 1946, when sorting was predominantly done by hand at the sorting frame, was of a future system in which the national flow of mail would pass through large, mechanised sorting offices containing machines capable of “reading” each address. Their ultimate goal was to have human labour largely replaced within a generation by the new system, in which the public would cooperate by adding a code when addressing their letters to enable both interpretation and handling to be processed by machines.

As we have seen, as both postmen’s wages and the national volume of mail continued to rise over this period, there was good incentive to pursue these aims and to make what was termed the “code-sort concept” a reality. In the 1950s, the formative years of postal coding theory and practice, new lines of research pursued by GPO engineers helped lock particular characteristics into today’s familiar alpha-numeric postcode, as records held by the BPMA make clear. In particular the files of the Mechanical Aids Committee (MAC) and its subcommittees, which guided GPO policy on letter mechanisation and postcoding, show that choosing from many possible alternative code designs was no simple business.

A colour print of Mount Pleasant sorting office. The print is done in a comical style, portraying the 'un-pleasant' nature of the sorting office with its electronic sorting machine. Post, post bags and postmen are being flung through the office while two managers in suits stand in the middle. Outside is a post van with 'ER' on the side. (Circa 1965)

One aspect of 1950s postal engineering involved trying to understand the psychological processes at work during the act of sorting letters when operating the new experimental machines then being trialled. This was an important step in both the development of the postcode and also in the GPO’s understanding of the so-called “man-machine interface”. Although at the outset it was hoped optical character recognition technology (OCR) might develop to the point of being able to reliably “read” handwritten postcodes, it was known early on that this was decades away at best. Machines for preparing and stacking the mail were then in development and, through an intricate arrangement of rollers, belts, diverters and memory storage, there were excellent prospects for an economical and reliable automatic sorting machine.

The problem was uniting these two phases of sorting – initial preparation of mail entering a sorting office into uniform piles followed by automatic sorting of that mail for particular destinations. In the absence of OCR, people stationed at keyboards (the man-machine interface) would still be needed to read the postcodes on letters and mark each with the correct machine-readable binary imprint. In any national code-sort system this would mean many millions of keystrokes every working day which placed a great financial premium on finding the most efficient arrangement of characters when designing the optimal postcode. A format acceptable to the public and major commercial mail users and also capable of accommodating the required address information was needed. But of no less importance was arriving at a format agreeable to the postman at his keyboard. An optimal format needed to encourage the most efficient possible coordination of hand, eye and brain.

Sir Gordon Radley

A key figure in this regard was Sir Gordon Radley who took over the Mechanical Aids Committee (MAC) in 1955. This coincided with his appointment as Director General (Secretary to the Post Office), the first engineer to hold this office. Born in Birmingham in 1898, Radley gained his Doctorate in Engineering and served with the Royal Engineers during WWI. He joined the GPO in 1920 where he gained successive promotions through the Engineering Department. During WWII he and fellow telephone engineer Tommy Flowers made significant contributions to code-breaking at Bletchley Park and the design of “Colossus”. He spent ten years as Controller of Dollis Hill Research Station, the GPO centre for technological research, where he earned international fame for leading the development of the first transatlantic submarine cable and helping to invent the hearing aid.

When Radley chaired his first MAC meeting on 16 November 1955, he spoke of injecting more efficiency and pro-activity into the mechanisation field, issuing tighter deadlines and drafting in more senior staff. He oversaw the continuation of various long-term lines of technical enquiry and wished to see quicker progress in the development of postcodes, identifying the coding of letters by fluorescent marks as a priority project. Here, he encouraged Mr. A. Crisswell, a Deputy Regional Postal Director who headed the coding study group, to take a more liberal approach and worry less about the financial prospects of new ideas. Crisswell was directed to increase collaboration with operational experts in the Postal Services Department and to specify the desired characteristics of a code and to consult mathematicians specialising in coding theory.

Radley’s personal intervention into developing codes came as a series of questions posed in April 1956. A series of field trials with the Single Position Letter Sorting Machine (SPLSM) were then underway at Bath. There, postmen were trained to operate the machine’s keyboard to which letters were presented for processing, in which a memorised list of two-letter codes (denoting counties and towns) were added to the letters based on their addresses at between 32 and 52 items per minute. Their movements were filmed and then timed and analysed, prompting a series of questions on the MAC about how to deal with this data, with Radley leading the way. “Which kinds of codes are easiest to learn and use?” he asked. “What is the relationship between number of codes in a series and learning time?”, “What is the relationship between coding time and the number of possible codes to choose from?”, “How long does plural coding take relative to simple coding?” and “What is the best training method?”.

Single Position Letter Sorting Machine (1956-1986)

Such precise questions were used to direct new lines of research on the MAC as they sought to evolve better and better machines for letter sorting, of which the coding position was a vital “link”. The Bath trials and the manner in which their results were put to use by GPO engineers is just one early episode in a long history of ergonomic design for coding desks and added to a body of research into the physical and mental demands made upon postmen who sorted the mail. Radley’s questions might also be seen as illustrating the diversity of factors at play in choosing the most suitable code for the British postal service.

In this series of blog posts, Peter Sutton, PhD candidate researching the post-war history of technology and industrial relations in the British Postal Service, offers some reflections on the history of the modern postcode. The significance of the postcode and its origins in the post-1945 era are considered followed by some archival examples tracing different aspects of its design along its journey from a specialised engineering concept to a universally recognised geographical referencing tool.

Royal Mail poster Poster relating to service standards (1983)

In some ways the postcode is simple, an intentional characteristic that was given priority during its design in the post-war era. It needed to be quickly understood by postmen and easily remembered by the public. Its function as an abbreviator of addresses made it simple almost by definition. Equally, the business strategy behind the postcode project was at its core straightforward. In 1968 a manual sorting system prevailed in which, it was estimated, letters were sorted on average 3.2 times during their journey. A letter finding itself on a more tortuous routing might be handled five or six times before delivery. With almost 30 million letters handled at the sorting frame every working day, and as wages rose steadily in real terms in the post-war era, this was an increasingly expensive arrangement. After a string of successful trials in the 50s and 60s, sorting machines capable of “reading” a series of phosphor dots offered a partial solution. If a letter, upon entering the system, could first be marked with the machine readable dots containing sorting instructions then, officials at GPO Headquarters reasoned, all subsequent stages of sorting could be automated. In this scenario, human labour in the sorting process would be mostly confined to making an initial imprint on each envelope by a human operator reading the postcode at a “coding desk” and punching the information into a keyboard. Subsequent re-sorting could then be done by machine, eliminating much duplication of effort. The modern postcode, from this perspective, began life as a crucial component of what was hoped would one day become an all-encompassing system of integrated, automated sorting offices equipped with “robot sorters”.

If the underlying economics of the postcode are simple, the course of its design was not. This was a long-term and highly complex process which encompassed, among other things, the design of a binary machine language, basic research in chemistry, the mathematics of code theory, field trials in which sorting staff and psychologists had their input, and considerable research into the needs of businesses. The likely response of the public was analysed as were many elements of the postal service itself and the entire effort was also seen in an international context as an interest in code-sorting was taken up in Europe, America and Japan. Reflecting on the origins of the code, the PO explained during a 1976 parliamentary inquiry that strict parameters were established upon its design in the 1950s. The public needed something memorable and uniform and compatible with the old city district codes. Operationally, the code needed flexibility to accommodate variations and ad hoc revisions to circulation and delivery, and would have to form two parts reflecting the outward and inward phases of sorting. (Outward sorting directs mail to a different city or region, while inward sorting directs mail to a particular address.) The characteristics required of the code therefore had to mesh with the demands of various economic and psychological aspects of letter writing. This was not forgotten by Post Office officials when asked to reflect on the origins of the code during a 1970s Parliamentary Inquiry into the Postal Service. “This financial requirement” they remembered, “was a major factor in determining the type of equipment developed which affected the shape of the postcode. For example, the method envisaged for imprinting the codes in machine language was by means of an operator using a keyboard; and there was a limit to the capacity of the code ‘translator’ device [the “brain” of a mechanised sorting suite] that could be developed at economic cost.” (Cmnd. 6954, Appendix to the Carter Report (Post Office Review), 1977.)

Think, therefore, of your own postcode. As I have mentioned, it will have two parts. There will be a maximum of seven characters. The first part – the “outward” part – will specify a district within your wider mail delivery area. (For instance a house in York’s third delivery district becomes “YO3”.) This part was designed for long-term flexibility in an evolving mail circulation system and might have three or four characters. However the second part – the “inward” part – is a standardised allocation allowing for local, computerised delivery scheduling. It will have one numeral followed by two alpha characters, representing the sub-district, street and group of houses for your address. All of these features were deliberately chosen and could have been different but for historic decisions taken in light of the geography, transport distribution and population density of 1960s Britain. This, by the way, is one reason why Australian, Japanese and American postcodes all differ in their format. All were created for the same simple purpose of making addresses easier to read by machines. But equally, for each, design requirements and restrictions have differed from country to country in quite complex ways.

Poster promoting postcode usage (c. 1980)

This and the previous post have very briefly outlined some of the general principals and historic background which have helped shape the design of modern postcodes. In the next post we go back to the 1950s to look a bit closer at the early history of sorting machines and how engineers helped create the code.

In this series of blog posts, Peter Sutton, PhD candidate researching the post-war history of technology and industrial relations in the British Postal Service, offers some reflections on the history of the modern postcode. The significance of the postcode and its origins in the post-1945 era are considered followed by some archival examples tracing different aspects of its design along its journey from a specialised engineering concept to a universally recognised geographical referencing tool.

Poster promoting postcode usage, circa 1978

We think about postcodes regularly. Perhaps, as it gets lost in the noise of everyday activity, we aren’t aware of how often we do it or at least how many ways we benefit from them. In our correspondence, by ‘phone, in the car and in all manner of ways online, we engage with them in the everyday sense. A moment’s thought reveals the wide-ranging uses of postcodes, and yet, as a tool, it has many more hidden and no less important applications. After all, they are today used in demographic profiling, monitoring crime levels, determining insurance premiums, data analysis and marketing techniques – not to mention their role in house prices or catchment areas for schools and healthcare. In fact trying to list all applications of the postcode has been made virtually impossible by the internet where ordering a pizza or a beanbag can be done with little more than a postcode and a credit card. The geographers Jonathan Raper, David Rhind and John Shepherd have pointed to its diverse usage whilst acknowledging its postal origins in their book Postcodes: The New Geography (1992). “We need”, they write in their introduction, “something that provides the ability to divide up the country into small areas or large ones, is simple to understand, can be related to everyday experience and is easily handled by computers as well as human beings. This is the Postcode, born out of the postal system and founded upon postal addresses.” And yet it is a relatively recent invention. It differs in its form from country to country, but in all cases (including the British with its familiar, even reassuring, two-part alpha-numeric arrangement) it did not exist until the 1960s. Not, at least, in anything like a modern, widespread or standardised sense.

Informational handstamp about using postcodes. (20th Century)

So where did the postcode come from? In Britain, Royal Mail can take the credit, or, as it was then, the General Post Office. Some codes were used locally in the nineteenth century postal service, such as in London where compass point abbreviations had evolved by the end of the First World War to include several sub-districts helping to simplify the Capital’s sorting and delivery. However it was not until after 1945 that a systematic, national coding scheme was seriously considered, as new types of technology and logistical techniques combined with growing financial pressures to create a powerful incentive to code the country. It was originally intended to reduce the information contained in a written address into a machine-readable code in order to help increase the speed and reduce the cost of mail delivery, and it continues to serve this purpose today. Its design began in earnest in the 1950s, primarily to enable the spread of mechanised sorting, leading to a major trial at Norwich from 1959 and then to a period from 1965-1972 when every British address received a code. The timing of this coincided with an early phase in the first national mechanisation programme known as the Letter Post Plan in which the national mail flow was concentrated onto large mechanised sorting offices. The modern postcode therefore has its origins in the long history of postal mechanisation and automation.

Royal Mail poster about using postcodes, circa 1980

In the next post we delve a little further into the history of the postcode after 1945, summarising the simple economics that made it such an attractive scheme to Post Office officials as well as highlighting the diverse range of factors that helped shape its design.